The present invention relates to wastewater treatment and, more particularly, to an apparatus for treating wastewater from catering industry such as restaurants, caterers, etc.
Improperly managed oil and grease from restaurants has become a significant problem for wastewater collection and treatment systems. Fats, oils, and grease (often referred to as FOG) are not soluble; meaning they do not mix well with water. Due to this, FOG floats on water and clings to surface areas void of water. If excessive FOG in a wastewater is directly discharged into a sewer collection system, FOG may be accumulated therein, thus causing potential blockage of the piping in the collection system. Also, there exist serious sludge foaming problems in the secondary sewage treatment works.
Consequently, many local codes require the removal of FOG from wastewater prior to go down the drain.
It is well known that oil/grease separators are capable of separating immiscible liquids having different specific gravities. Known oil/grease separators have been disclosed in many U.S. Patents, such as U.S. Pat. No. 5,861,098. However, such some systems are complex, energy demanding, expensive to build and operate and not suitable for discharging to the sewer system.
Several modifications of wastewater treatment processes have been developed: 1. aerobic (activated sludge process, lagoon systems, and biofiltration); 2. anaerobic (various attached and suspended growth processes); and 3. coupled anaerobic-aerobic systems. However, for wastewater from catering industry such as restaurants etc, due to the space and cost constraints as well as the characteristics of the wastewater, conventional biotreatment technology for wastewater is not applicable.
Accordingly, there is a need for an on-site, low cost and space-saving biotreatment facility for treating a high concentration of FOG.
The present invention is an apparatus which has been developed to meet the needs discussed above and overcome the drawbacks of the prior art.
It is an object of the invention, therefore, to provide an apparatus for treating wastewater from catering industry, particularly from the restaurants. Specifically, the apparatus comprises a single reactor tank, said reactor tank comprising:
(a) an inlet arranged to feed wastewater influent into said reactor tank;
(b) an open and substantially oil-tight tank therein an upper oil film zone, anoxic zone below said oil film zone and an anaerobic zone below said anoxic zone are divided; said anoxic and anaerobic zones are layered, but without clearly defined phase separation between them; an upper net is located in said anoxic zone and a lower net is located in said anaerobic zone; and some plastic suspending media as biocarriers are introduced into said anoxic and anaerobic zones;
(c) an outlet arranged to discharge the effluent from said reactor tank to the main drain.
The apparatus in accordance with present invention further comprises:
a second outlet for draining the excessive FOG; a third outlet for dumping the excessive sludge; a circulation conduit with a pump located between the bottom of said reactor tank and said lower net and fluidly connected to said inlet pipe.
The apparatus in accordance with the present invention further comprises:
an upflow back wash conduit which is placed near the bottom of said reactor tanks and has xc2xc diameter of said inlet pipe.
The apparatus in accordance with the present invention further comprises:
a flow equalization tank for storing and controlling of the wastewater.
It is contemplated that the present apparatus will be employed for treating wastewater drained from restaurant sinks and the treated wastewater may be directly discharged to conventional sewers in an environmentally-safe manner in compliance with typing local codes. The oil and grease removed from the wastewater is held in a convenient storage vessel for ultimate disposal.
In addition to improved efficiency in separating oil and grease from wastewater, the present apparatus advantageously requires minimal space, energy and operation costs. Further, biological sludge produced therein is much lower than aeration systems and is suitable for sludge thickening and dewatering.
One embodiment of the invention will now be described in conjunction with the accompanying drawings in which: